Why does Blender crash when I select Skin for my 3D model?
I think you might not know the purpose of the Skin Modifier. With it, any vertex is kind of a tubular node connected to the other ones. It's for making quick base model like the image below:



Applied to a complex model, would take several minutes to process it. And the results are not pretty good though. Here you can see a cube and a Suzzane with the Skin Modifier. Suzzane completely freezed the aplication for 2 minutes. 



The use of the Skin Modifier is covered in its wiki page. 

At this point, I think this is not what you want to accomplish. As you have animation and rigging tags in your question, I think you need the Armature Modifier for make your character rig. Armature Modifier is named Skin in 3ds Max, maybe that's why you made this mistake (if you did).

It looks that I haven't clarify that enough: in this case, you need to create an Armature (a rig in Blender) and use the Armature Modifier (like Skin in 3ds Max) in your character's mesh.